Radial back-curling thermoelastic ink jet printing mechanism

ABSTRACT

A nozzle arrangement for an ink jet printhead includes a wafer substrate having a nozzle chamber defined therein. The nozzle arrangement has a nozzle chamber wall that defines an ink ejection port and a rim about the ink ejection port. A series of radially positioned actuators are attached to the nozzle rim and extend radially from the rim to form a portion of the nozzle chamber wall adjacent the rim. Each actuator is configured so that a radially outer edge of each actuator is displaceable into the chamber, upon actuation of the actuator and so that, upon such displacement, a pressure within the nozzle chamber is increased, resulting in the ejection of ink from the ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

US PATENT/ PATENT APPLICATION (CLAIMING RIGHT OF CROSS-REFERENCEDPRIORITY FROM AUSTRALIAN AUSTRALIAN PROVISIONAL PATENT PROVISIONALAPPLICATION No. APPLICATION) DOCKET No. PO7991 09/113,060 ART01 PO850509/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO801709/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO803209/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO803109/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO797909/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO798209/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO798009/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO801609/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO793909/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO798709/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO802009/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO800009/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799009/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO798109/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO802609/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO939409/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO939809/112,792 ART60 PO9399 6,106,147 ART61 PO9400 09/112,790 ART62 PO940109/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO940509/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP237009/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01PO8005 09/113,103 Fluid02 PO9404 09/113,101 FluidO3 PO8066 09/112,751IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827IJM04 PO8054 09/112,828 IJM05 PO8065 6,071,750 IJM06 PO8055 09/113,108IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 6,111,754IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774IR18 PP0883 09/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092IR21 PO8006 6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062MEMS04 PO8010 6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947 6,067,797MEMS07 PO7944 09/113,080 MEMS09 PO7946 6,044,646 MEMS10 PO939309/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

S

TATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Notapplicable.

FIELD OF THE INVENTION

The present invention relates to the field of inkjet printing and fluidpumping systems and, in particular, discloses a radial back-curlingthermoelastic inkjet printer.

BACKGROUND OF THE INVENTION

Many different types of printing mechanisms have been invented, a largenumber of which are presently in use. The known forms of printers have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop-on-demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques of ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. Theutilization of a continuous stream of ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including a step wherein the ink jet streamis modulated by a high frequency electro-static field so as to causedrop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat.No.3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode ofpiezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 whichdiscloses a piezoelectric push mode actuation of the ink jet stream andFischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode typeof piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing.

The ink jet printing techniques include those disclosed by Endo et al inGB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both theaforementioned references disclose ink jet printing techniques whichrely upon the activation of an electrothermal actuator which results inthe creation of a bubble in a constricted space, such as a nozzle, whichthereby causes the ejection of ink from an aperture connected to theconfined space onto a relevant print media. Printing devices utilizingthe electro-thermal actuator are manufactured by manufacturers such asCanon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction, operation, durability andconsumables.

In accordance with a first aspect of the present invention, there isprovided nozzle arrangement for use with an ink jet printhead, thearrangement comprising: a nozzle chamber for the storage of ink to beejected; an ink ejection port having a rim formed on one wall of thechamber; and a series of actuators attached to the nozzle rim, andforming a portion of the wall of the nozzle chamber adjacent the rim,the actuators further being actuated in unison to eject ink from thenozzle chamber via the ink ejection port.

The actutators can each include a surface which bends inwards towardsthe centre of the nozzle chamber upon actuation. The actuators arepreferably actuated by means of a thermal actuators device. The thermalactuator device can comprise a conductive resistive heating elementencased within a second material having a high coefficient of thermalexpansion. The element can be serpentine shaped to allow forsubstantially unhindered expansion of the second material. The actuatorsare preferably arranged radially around the nozzle rim.

The actuators can form a membrane between the nozzle chamber and anexternal atmosphere of the arrangement. The actuators can bend away fromthe external atmosphere to cause an increase in pressure within thenozzle chamber thereby initiating a consequential ejection of ink fromthe nozzle chamber. The actuators can bend towards a central axis of theejection nozzle.

The ink jet nozzle arrangement can be formed on a wafer utilizingmicro-electro mechanical techniques and further can comprise an inksupply channel interconnected to the nozzle chamber. The ink supplychannel may be etched through the wafer. The ink jet nozzle arrangementcan include the ink ejection nozzle supported by a series of struts andthe actuators are preferably further interconnected to the nozzle rimand the struts can include a conductive power rail for supplyingelectrical power to the actuators.

The arrangement can be formed adjacent to neighbouring arrangements soas to form a pagewidth printhead.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIGS. 1-3 are schematic sectional views illustrating the operationalprinciples of the preferred embodiment;

FIG. 4(a) and FIG. 4(b) are again schematic sections illustrating theoperational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzlearrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 illustrate side perspective views, partly in section,illustrating the manufacturing steps of the preferred embodiments; and

FIG. 14 illustrates an array of ink jet nozzles formed in accordancewith the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23;and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, ink is ejected out of a nozzle chamber viaan ink ejection port as the result of the utilzation of a series ofradially positioned thermal actuator devices that are arranged aroundthe ink ejection port and are activated so as to pressurize the inkwithin the nozzle chamber thereby causing ink ejection.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basicoperational principles of the preferred embodiment. FIG. 1 illustrates asingle nozzle arrangement 1 in a quiescent state. The arrangement 1includes a nozzle chamber 2 which is normally filled with ink to form ameniscus 3 in an ink ejection port 4. The nozzle chamber 2 is formedwithin a wafer 5. The nozzle chamber 2 is in fluid communication with anink supply channel 6 which is etched through the wafer 5 using a highlyisotropic plasma etching system. A suitable etcher is the AdvanceSilicon Etch (ASE) system available from Surface Technology Systems ofthe United Kingdom.

The nozzle arrangement 1 includes a series of radially positionedthermoactuator devices 8, 9 about the ink ejection port 4. These devicescomprise a series of polytetrafluoroethylene (PTFE) actuators having aninternal serpentine copper core, which is positioned so that uponheating of the copper core, the subsequent expansion of the surroundingTeflon results in a generally inward movement of radically outer edgesof the actuators 8, 9. Hence, when it is desired to eject ink from theink ejection nozzle 4, a current is passed through the actuators 8, 9which results in the bending as illustrated in FIG. 2. The bendingmovement of actuators 8, 9 results in a substantial increase in pressurewithin the nozzle chamber 2. The rapid increase in pressure in nozzlechamber 2, in turn results in a rapid expansion of the meniscus 3 asillustrated in FIG. 2.

The actuators 8, 9 are briefly activated only and subsequentlydeactivated so that the actuators 8, 9 rapidly return to their originalpositions as shown in FIG. 3. This results in a general inflow of inkand a necking and breaking of the meniscus 3 resulting in the ejectionof a drop 12. The necking and breaking of the meniscus 3 is aconsequence of a forward momentum of the ink of the drop 12 and anegative pressure created as a result of the return of the actuators 8,9 to their original positions. The return of the actuators 8, 9 alsoresults in a general inflow of ink in the direction of an arrow so fromthe supply channel 6. Surface tension effects results in a return of thenozzle arrangement 1 to the quiescent position as illustrated in FIG. 1.

FIGS. 4(a) and 4(b) illustrate a principle of operation of the thermalactuators 8, 9. Each thermal 8, 9 actuator is preferably constructedfrom a material 14 having a high coefficient of thermal expansion.Embedded within the material 14 is a series of heater elements 15 whichcan be a series of conductive elements designed to carry a current. Theconductive elements 15 are heated by passing a current through theelements 15 with the heating resulting in a general increase intemperature in the area around the heating elements 15. The increase intemperature causes a corresponding expansion of the PTFE which has ahigh coefficient of thermal expansion. Hence, as illustrated in FIG.4(b), the PTFE is bent generally in a inward direction.

Turning now to FIG. 5, there is illustrated a side perspective view ofone nozzle arrangement constructed in accordance with the principlespreviously outlined. The nozzle chamber 2 is formed by an isotropicsurface etch of the wafer 5. The wafer 5 includes a CMOS layer 21including all the required power and drive circuits. Further, theactuators 8, 9 are fabricated as a series of leaf or petal typeactuators each having an internal copper or aluminum core 17 which windsin a serpentine nature to provide for substantially unhindered expansionof the actuator device. The operation of the actuators 8, 9 is asdescribed earlier with reference to FIG. 4(a) and FIG. 4(b) such that,upon activation, the petals 8 bend inwardly as previously described. Theink supply channel 6 is created with a deep silicon back edge of thewafers utilizing a plasma etcher or the like. The copper or aluminumcoil 17 defines a complete circuit. A central arm 18 which includes bothmetal and PTFE portions provides main structural support for theactuators 8, 9 in addition to providing a current trace for theconductive elements.

Steps of the manufacture of the nozzle arrangement 1 are described withreference to FIG. 6 to FIG. 13. The nozzle arrangement 1 is preferablyconstructed utilizing microelectromechanical (MEMS) techniques and caninclude the following construction techniques:

As shown initially in FIG. 6, the initial processing starting materialis a standard semi-conductor wafer 20 having a complete CMOS level 21 tothe first level metal. The first level metal includes portions 22 whichare utilized for providing power to the thermal actuators 8,9.

The first step, as illustrated in FIG. 7, is to etch a nozzle regiondown to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene(PTFE) is deposited and etched to define vias 24 for interconnectingmultiple levels.

Next, as illustrated in FIG. 9, the second level metal layer isdeposited, masked and etched to form a heater structure 25. The heaterstructure 25 is connected at 26 with a lower aluminum layer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE isdeposited and etched to a depth of 1 μm utilizing a nozzle rim mask soas to form a nozzle rim 28 in addition to ink flow guide rails 29 whichinhibit wicking along the surface of the PTFE layer. The guide rails 29thin slots. Thus, surface tension effects result in minimal outflow ofink during operation from the slots.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzleand actuator mask to define an ejection nozzle port 30 and slots 31 and32.

Next, as illustrated in FIG. 12, the wafer is crystallographicallyetched on a <111> plane utilizing a standard crystallographic etchantsuch as KOH. The etching forms a chamber 32, directly below the inkejection port 30.

Next, turning to FIG. 13, the ink supply channel 6 is etched from a backof the wafer utilizing a highly anisotropic etcher such as the STSetcher from Silicon Technology Systems of the United Kingdom. An array36 of ink jet nozzles can be formed simultaneously with a portion of thearray 36 being illustrated in FIG. 14. A portion of the printhead isformed simultaneously and diced by the STS etching process. The array 36shown provides for four column printing with each separate columnattached to a different color ink supply channel which is supplied fromthe back of the wafer. Bond pads 37 provide for electrical control ofthe ejection mechanism.

In this manner, large pagewidth printheads can be formulated to providefor a drop on demand ink ejection mechanism.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed along thefollowing steps:

1. Using a double sided polished wafer 20, complete a 0.5 micron, onepoly, 2 metal CMOS process to form layer 21. This step is shown in FIG.16. For clarity, these diagrams may not be to scale, and may notrepresent a cross section though any single plane of the nozzle. FIG. 15is a key to representations of various materials in these manufacturingdiagrams, and those of other cross referenced ink jet configurations.

2. Etch the CMOS oxide layers down to silicon or second level metalusing Mask 1. This mask defines the nozzle cavity and the edge of thechips. This step is shown in FIG. 16.

3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treatthe surface of this polymer for PTFE adherence.

4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 60.

5. Etch the PTFE and CMOS oxide layers to second level metal using Mask2. This mask defines the contact vias 24 for the heater electrodes. Thisstep is shown in FIG. 17.

6. Deposit and pattern 0.5 microns of gold 61 using a lift-off processusing Mask 3. This mask defines the heater pattern. This step is shownin FIG. 18.

7. Deposit 1.5 microns of PTFE 62.

8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim28 and the ink flow guide rails 29 at the edge of the nozzle chamber.This step is shown in FIG. 19.

9. Etch both layers of PTFE and the thin hydrophilic layer down tosilicon using Mask 5. This mask defines a gap 64 at the edges of theactuators 8, 9, and the edge of the chips. It also forms the mask forthe subsequent crystallographic etch. This step is shown in FIG. 20.

10. Crystallographically etch the exposed silicon using KOH. This etchstops on <111> crystallographic planes 65, forming an inverted squarepyramid with sidewall angles of 54.74 degrees. This step is shown inFIG. 21.

11. Back-etch through the silicon wafer (with, for example, an ASEAdvanced Silicon Etcher from Surface Technology Systems) using Mask 6.This mask defines the ink supply channel 60 which are etched through thewafer 5. The wafer 5 is also diced by this etch. This step is shown inFIG. 22.

12. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets at the back of the wafer.

13. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

14. Fill the completed printheads with ink 66 and test them. A fillednozzle is shown in FIG. 23.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The print heads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 above which matches the docket numbers in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal ♦ Largeforce ♦ High power ♦ Canon Bubblejet bubble heater heats the ink togenerated ♦ Ink carrier 1979 Endo et al GB above boiling point, ♦ Simplelimited to water patent 2,007,162 transferring significant construction♦ Low efficiency ♦ Xerox heater-in- heat to the aqueous ♦ No movingparts ♦ High pit 1990 Hawkins et ink. A bubble ♦ Fast operationtemperatures al U.S. Pat. No. 4,899,181 nucleates and quickly ♦ Smallchip area required ♦ Hewlett-Packard forms, expelling the required foractuator ♦ High mechanical TIJ 1982 Vaught et ink. stress al U.S. Pat.No. 4,490,728 The efficiency of the ♦ Unusual process is low, withmaterials required typically less than ♦ Large drive 0.05% of theelectrical transistors energy being ♦ Cavitation causes transformed intoactuator failure kinetic energy of the ♦ Kogation reduces drop. bubbleformation ♦ Large print heads are difficult to fabricate Piezo- Apiezoelectric crystal ♦ Low power ♦ Very large area ♦ Kyser et al U.S.Pat. No. electric such as lead consumption required for actuator3,946,398 lanthanum zirconate ♦ Many ink types ♦ Difficult to ♦ ZoltanU.S. Pat. No. (PZT) is electrically can be used integrate with 3,683,212activated, and either ♦ Fast operation electronics ♦ 1973 Stemmeexpands, shears, or ♦ High efficiency ♦ High voltage U.S. Pat. No.3,747,120 bends to apply drive transistors ♦ Epson Stylus pressure tothe ink, required ♦ Tektronix ejecting drops. ♦ Full pagewidth ♦ IJ04print heads impractical due to actuator size ♦ Requires electricalpoling in high field strengths during manufacture Electro- An electricfield is ♦ Low power ♦ Low maximum ♦ Seiko Epson, strictive used toactivate consumption strain (approx. Usui et alk JP electrostriction in♦ Many ink types 0.01%) 253401/96 relaxor materials such can be used ♦Large area ♦ IJ04 as lead lanthanum ♦ Low thermal required for actuatorzirconate titanate expansion due to low strain (PLZT) or lead ♦ Electricfield ♦ Response speed magnesium niobate strength required is marginal(˜10 (PMN). (approx. 3.5 V/μm) μs) can be generated ♦ High voltagewithout difficulty drive transistors ♦ Does not require requiredelectrical poling ♦ Full pagewidth print heads impractical due toactuator size Ferro- An electric field is ♦ Low power ♦ Difficult to ♦IJ04 electric used to induce a phase consumption integrate withtransition between the ♦ Many ink types electronics antiferroelectric(AFE) can be used ♦ Unusual and ferroelectric (FE) ♦ Fast operationmaterials such as phase. Perovskite (<1 μs) PLZSnT are materials such astin ♦ Relatively high required modified lead longitudinal strain ♦Actuators require lanthanum zirconate ♦ High efficiency a large areatitanate (PLZSnT) ♦ Electric field exhibit large strains of strength ofaround 3 up to 1% associated V/μm can be readily with the AFE to FEprovided phase transition. Electro- Conductive plates are ♦ Low power ♦Difficult to ♦ IJ02, IJ04 static plates separated by a consumptionoperate electrostatic compressible or fluid ♦ Many ink types devices inan dielectric (usually air). can be used aqueous Upon application of a ♦Fast operation environment voltage, the plates ♦ The electrostaticattract each other and actuator will displace ink, causing normally needto be drop ejection. The separated from the conductive plates may ink bein a comb or ♦ Very large area honeycomb structure, required to achieveor stacked to increase high forces the surface area and ♦ High voltagetherefore the force. drive transistors may be required ♦ Full pagewidthprint heads are not competitive due to actuator size Electro- A strongelectric field ♦ Low current ♦ High voltage ♦ 1989 Saito et al, staticpull is applied to the ink, consumption required U.S. Pat. No. 4,799,068on ink whereupon ♦ Low temperature ♦ May be damaged ♦ 1989 Miura et al,electrostatic attraction by sparks due to air U.S. Pat. No. 4,810,954accelerates the ink breakdown ♦ Tone-jet towards the print ♦ Requiredfield medium. strength increases as the drop size decreases ♦ Highvoltage drive transistors required ♦ Electrostatic field attracts dustPermanent An electromagnet ♦ Low power ♦ Complex ♦ IJ07, IJ10 magnetdirectly attracts a consumption fabrication electro- permanent magnet, ♦Many ink types ♦ Permanent magnetic displacing ink and can be usedmagnetic material causing drop ejection. ♦ Fast operation such asNeodymium Rare earth magnets ♦ High efficiency from Boron (NdFeB) with afield strength ♦ Easy extension required. around 1 Tesla can be fromsingle nozzles ♦ High local used. Examples are: to pagewidth printcurrents required Samarium Cobalt heads ♦ Copper (SaCo) and magneticmetalization should materials in the be used for long neodymium ironboron electromigration family (NdFeB, lifetime and low NdDyFeBNb,resistivity NdDyFeB, etc) ♦ Pigmented inks are usually infeasible ♦Operating temperature limited to the Curie temperature (around 540 K.)Soft A solenoid induced a ♦ Low power Complex ♦ IJ01, IJ05, IJ08,magnetic magnetic field in a soft consumption fabrication IJ10, IJ12,IJ14, core electro- magnetic core or yoke ♦ Many ink types ♦ Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such ♦ Fast operation CMOS fab such as aselectroplated iron ♦ High efficiency NiFe, CoNiFe, or alloys such asCoNiFe ♦ Easy extension CoFe are required [1], CoFe, or NiFe from singlenozzles ♦ High local alloys. Typically, the to pagewidth print currentsrequired soft magnetic material heads ♦ Copper is in two parts, which ♦metalization should are normally held be used for long apart by aspring. electromigration When the solenoid is lifetime and low actuated,the two parts resistivity attract, displacing the ♦ Electroplating isink. required ♦ High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force ♦ Low power ♦ Forceacts as a ♦ IJ06, IJ11, IJ13, force acting on a current consumptiontwisting motion IJ16 carrying wire in a ♦ Many ink types ♦ Typically,only a magnetic field is can be used quarter of the utilized. ♦ Fastoperation solenoid length This allows the ♦ High efficiency providesforce in a magnetic field to be ♦ Easy extension useful directionsupplied eternally to from single nozzles ♦ High local the print head,for to pagewidth print currents required example with rare heads ♦Copper earth permanent metalization should magnets. be used for longOnly the current electromigration carrying wire need be lifetime and lowfabricated on the print- resistivity head, simplifying ♦ Pigmented inksmaterials are usually requirements. infeasible Magneto- The actuatoruses the ♦ Many ink types ♦ Force acts as a ♦ Fischenbeck, strictiongiant magnetostrictive can be used twisting motion U.S. Pat. No.4,032,929 effect of materials ♦ Fast operation ♦ Unusual ♦ IJ25 such asTerfenol-D (an ♦ Easy extension materials such as alloy of terbium, fromsingle nozzles Terfenol-D are dysprosium and iron to pagewidth printrequired developed at the Naval heads ♦ High local Ordnance Laboratory,♦ High force is currents required hence Ter-Fe-NOL). available ♦ CopperFor best efficiency, the metalization should actuator should be pre- beused for long stressed to approx. 8 electromigration MPa. lifetime andlow resistivity ♦ Pre-stressing may be required Surface Ink underpositive ♦ Low power ♦ Requires ♦ Silverbrook, EP tension pressure isheld in a consumption supplementary force 0771 658 A2 and reductionnozzle by surface ♦ Simple to effect drop related patent tension. Thesurface construction separation applications tension of the ink is ♦ Nounusual ♦ Requires special reduced below the materials required in inksurfactants bubble threshold, fabrication ♦ Speed may be causing the inkto ♦ High efficiency limited by surfactant egress from the ♦ Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is ♦ Simple ♦ Requires ♦ Silverbrook,EP reduction locally reduced to construction supplementary force 0771658 A2 and select which drops are ♦ No unusual to effect drop relatedpatent to be ejected. A materials required in separation applicationsviscosity reduction can fabrication ♦ Requires special be achieved ♦Easy extension ink viscosity electrothermally with from single nozzlesproperties most inks, but special to pagewidth print ♦ High speed isinks can be engineered heads difficult to achieve for a 100:1 viscosity♦ Requires reduction. oscillating ink pressure ♦ A high temperaturedifference (typically 80 degrees) is required Acoustic An acoustic waveis ♦ Can operate ♦ Complex drive ♦ 1993 Hadimioglu generated and withouta nozzle circuitry et al, EUP 550,192 focussed upon the plate ♦ Complex♦ 1993 Elrod et al, drop ejection region. fabrication EUP 572,220 ♦ Lowefficiency ♦ Poor control of drop position ♦ Poor control of drop volumeThermo- An actuator which ♦ Low power ♦ Efficient aqueous ♦ IJ03, IJ09,IJ17, elastic bend relies upon differential consumption operationrequires a IJ18, IJ19, IJ20, actuator thermal expansion ♦ Many ink typesthermal insulator on IJ21, IJ22, IJ23, upon Joule heating is can be usedthe hot side IJ24, IJ27, IJ28, used. ♦ Simple planar ♦ Corrosion IJ29,IJ30, IJ31, fabrication prevention can be IJ32, IJ33, IJ34, ♦ Small chiparea difficult IJ35, IJ36, IJ37, required for each ♦ Pigmented inksIJ38, IJ39, IJ40, actuator may be infeasible, IJ41 ♦ Fast operation aspigment particles ♦ High efficiency may jam the bend ♦ CMOS actuatorcompatible voltages and currents ♦ Standard MEMS processes can be used ♦Easy extension from single nozzles to pagewidth print heads High CTE Amaterial with a very ♦ High force can ♦ Requires special ♦ IJ09, IJ17,IJ18, thermo- high coefficient of be generated material (e.g. PTFE)IJ20, IJ21, IJ22, elastic thermal expansion ♦ Three methods of ♦Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFE depositionare deposition process, IJ28, IJ29, IJ30, polytetrafluoroethylen underdevelopment: which is not yet IJ31, IJ42, IJ43, e (PTFE) is used. Aschemical vapor standard in ULSI IJ44 high CTE materials deposition(CVD), fabs are usually non- spin coating, and ♦ PTFE depositionconductive, a heater evaporation cannot be followed fabricated from a ♦PTFE is a with high conductive material is candidate for low temperature(above incorporated. A 50 μm dielectric constant 350° C.) processinglong PTFE bend insulation in ULSI ♦ Pigmented inks actuator with ♦ Verylow power may be infeasible, polysilicon heater and consumption aspigment particles 15 mW power input ♦ Many ink types may jam the bendcan provide 180 μN can be used actuator force and 10 μm ♦ Simple planardeflection. Actuator fabrication motions include: ♦ Small chip area Bendrequired for each Push actuator Buckle ♦ Fast operation Rotate ♦ Highefficiency ♦ CMOS compatible voltages and currents ♦ Easy extension fromsingle nozzles to pagewidth print heads Conduct-ive A polymer with ahigh ♦ High force can ♦ Requires special ♦ IJ24 polymer coefficient ofthermal be generated materials themo- expansion (such as ♦ Very lowpower development (High elastic PITE) is doped with consumption CTEconductive actuator conducting substances ♦ Many ink types polymer) toincrease its can be used ♦ Requires a PTFE conductivity to about 3 ♦Simple planar deposition process, orders of magnitude fabrication whichis not yet below that of copper. ♦ Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator ♦ PTFEdeposition when resistively ♦ Fast operation cannot be followed heated.♦ High efficiency with high Examples of ♦ CMOS temperature (aboveconducting dopants compatible voltages 350° C.) processing include: andcurrents ♦ Evaporation and Carbon nanotubes ♦ Easy extension CVDdeposition Metal fibers from single nozzles techniques cannot Conductivepolymers to pagewidth print be used such as doped heads ♦ Pigmented inkspolythiophene may be infeasible, Carbon granules as pigment particlesmay jam the bend actuator Shape A shape memory alloy ♦ High force is ♦Fatigue limits ♦ IJ26 memory such as TiNi (also available (stressesmaximum number alloy known as Nitinol - of hundreds of MPa) of cyclesNickel Titanium alloy ♦ Large strain is ♦ Low strain (1%) developed atthe Naval available (more than is required to extend OrdnanceLaboratory) 3%) fatigue resistance is thermally switched ♦ Highcorrosion ♦ Cycle rate between its weak resistance limited by heatmartensitic state and ♦ Simple removal its high stiffness construction ♦Requires unusual austenic state. The ♦ Easy extension materials (TiNi)shape of the actuator from single nozzles ♦ The latent heat of in itsmartensitic state to pagewidth print transformation must is deformedrelative to heads be provided the austenic shape. ♦ Low voltage ♦ Highcurrent The shape change operation operation causes ejection of a ♦Requires pre- drop. stressing to distort the martensitic state LinearLinear magnetic ♦ Linear Magnetic ♦ Requires unusual ♦ IJ12 Magneticactuators include the actuators can be semiconductor Actuator LinearInduction constructed with materials such as Actuator (LIA), Linear highthrust, long soft magnetic alloys Permanent Magnet travel, and high(e.g. CONiFe) Synchronous Actuator efficiency using ♦ Some varieties(LPMSA), Linear planar also require Reluctance semiconductor permanentmagnetic Synchronous Actuator fabrication materials such as (LRSA),Linear techniques Neodymium iron Switched Reluctance ♦ Long actuatorboron (NdFeB) Actuator (LSRA), and travel is available ♦ Requires theLinear Stepper ♦ Medium force is complex multi- Actuator (LSA).available phase drive circuitry ♦ Low voltage ♦ High current operationoperation BASIC OPERATION MODE Actuator This is the simplest ♦ Simpleoperation ♦ Drop repetition ♦ Thermal inkjet directly mode of operation:the ♦ No external rate is usually ♦ Piezoelectric ink pushes inkactuator directly fields required limited to around 10 jet suppliessufficient ♦ Satellite drops kHz. However, this ♦ IJ01, IJ02, IJ03,kinetic energy to expel can be avoided if is not fundamental IJ04, IJ05,IJ06, the drop. The drop drop velocity is less to the method, but isIJ07, IJ09, IJ11, must have a sufficient than 4 m/s related to therefill IJ12, IJ14, IJ16, velocity to overcome ♦ Can be efficient, methodnormally IJ20, IJ22, IJ23, the surface tension. depending upon the usedIJ24, IJ25, IJ26, actuator used ♦ All of the drop IJ27, IJ28, IJ29,kinetic energy must IJ30, IJ31, IJ32, be provided by the IJ33, IJ34,IJ35, actuator IJ36, IJ37, IJ38, ♦ Satellite drops IJ39, IJ40, IJ41,usually form if drop IJ42, IJ43, IJ44 velocity is greater than 4.5 m/sProximity The drops to be ♦ Very simple print ♦ Requires close ♦Silverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced ♦ The drop the print media orapplications surface tension selection means transfer roller reductionof does not need to ♦ May require two pressurized ink). provide theenergy print heads printing Selected drops are required to separatealternate rows of the separated from the ink the drop from the image inthe nozzle by nozzle ♦ Monolithic color contact with the print printheads are medium or a transfer difficult roller.

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesElectro- The drops to be Very simple print Requires very Silverbrook, EPstatic pull printed are selected by head fabrication can highelectrostatic 0771 658 A2 and on ink some manner (e.g. be used fieldrelated patent thermally induced The drop Electrostatic fieldapplications surface tension selection means for small nozzle Tone-Jetreduction of does not need to sizes is above air pressurized ink).provide the energy breakdown Selected drops are required to separateElectrostatic field separated from the ink the drop from the may attractdust in the nozzle by a nozzle strong electric field. Magnetic The dropsto be Very simple print Requires Silverbrook, EP pull on ink printed areselected by head fabrication can magnetic ink 0771 658 A2 and somemanner (e.g. be used Ink colors other related patent thermally inducedThe drop than black are applications surface tension selection meansdifficult reduction of does not need to Requires very pressurized ink).provide the energy high magnetic fields Selected drops are required toseparate separated from the ink the drop from the in the nozzle by anozzle strong magnetic field acting on the magnetic ink. Shutter Theactuator moves a High speed (>50 Moving parts are IJ13, IJ17, IJ21shutter to block ink kHz) operation can required flow to the nozzle. Thebe achieved due to Requires ink ink pressure is pulsed reduced refilltime pressure modulator at a multiple of the Drop timing can Frictionand wear drop ejection be very accurate must be considered frequency.The actuator Stiction is energy can be very possible low Shuttered Theactuator moves a Actuators with Moving parts are IJ08, IJ15, IJ18, grillshutter to block ink small travel can be required IJ19 flow through agrill to used Requires ink the nozzle. The shutter Actuators withpressure modulator movement need only small force can be Friction andwear be equal to the width used must be considered of the grill holes.High speed (>50 Stiction is kHz) operation can possible be achievedPulsed A pulsed magnetic Extremely low Requires an IJ10 magnetic fieldattracts an ‘ink energy operation is external pulsed pull on ink pusher’at the drop possible magnetic field pusher ejection frequency. An Noheat Requires special actuator controls a dissipation materials for bothcatch, which prevents problems the actuator and the the ink pusher fromink pusher moving when a drop is Complex not to be ejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimu- actuator selects which operating speed phase and amplitude IJ08,IJ13, IJ15, lation) drops are to be fired The actuators must becarefully IJ17, IJ18, IJ19, by selectively may operate with controlledIJ21 blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 A2 and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet Any of the IJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium. drops is near or applications above air Tone-Jet breakdownDirect A magnetic field is Low power Requires Silverbrook, EP magneticused to accelerate Simple print head magnetic ink 0771 658 A2 and fieldselected drops of construction Requires strong related patent magneticink towards magnetic field applications the print medium. Cross Theprint head is Does not require Requires external IJ06, IJ16 magneticplaced in a constant magnetic materials magnet field magnetic field. Theto be integrated in Current densities Lorenz force in a the print headmay be high, current carrying wire manufacturing resulting in is used tomove the process electromigration actuator. problems Pulsed A pulsedmagnetic Very low power Complex print IJ10 magnetic field is used tooperation is possible head construction field cyclically attract a Smallprint head Magnetic paddle, which pushes size materials required in onthe ink. A small print head actuator moves a catch, which selectivelyprevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ109, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric ink jetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418- into a high travel, Generally high 423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High energy is Hewlett-Packard expansion actuatorchanges, construction in the typically required to Thermal Ink jetpushing the ink in all case of thermal ink achieve volume CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal toa direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14chip surface the print head surface. drops ejected required to achieveThe nozzle is typically normal to the perpendicular in the line ofsurface motion movement. Parallel to The actuator moves Suitable forFabrication IJ12, IJ13, IJ15, chip surface parallel to the print planarfabrication complexity IJ33, IJ34, IJ35, head surface. Drop FrictionIJ36 ejection may still be Stiction normal to the surface. Membrane Anactuator with a The effective Fabrication 1982 Howkins push high forcebut small area of the actuator complexity USP 4,459,601 area is used topush a becomes the Actuator size stiff membrane that is membrane areaDifficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes Rotary levers Device IJ05, IJ08, IJ13, therotation of some may be used to complexity IJ28 element, such a grill orincrease travel May have impeller Small chip area friction at a pivotrequirements point Bend The actuator bends A very small Requires the1970 Kyser et al when energized. This change in actuator to be made USP3,946,398 may be due to dimensions can be from at least two 1973 Stemmedifferential thermal converted to a large distinct layers, or to USP3,747,120 expansion, motion. have a thermal IJ03, IJ09, IJ10,piezoelectric difference across the IJ19, IJ23, IJ24, expansion,actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33, IJ34, otherform of relative IJ35 dimensional change. Swivel The actuator swivelsAllows operation Inefficient IJ06 around a central pivot. where the netlinear coupling to the ink This motion is suitable force on the paddlemotion where there are is zero opposite forces Small chip area appliedto opposite requirements sides of the paddle, e.g. Lorenz force.Straighten The actuator is Can be used with Requires careful IJ26, IJ32normally bent, and shape memory balance of stresses straightens whenalloys where the to ensure that the energized. austenic phase isquiescent bend is planar accurate Double The actuator bends in Oneactuator can Difficult to make IJ36, IJ37, IJ38 bend one direction whenbe used to power the drops ejected by one element is two nozzles. bothbend directions energized, and bends Reduced chip identical. the otherway when size. A small another element is Not sensitive to efficiencyloss energized. ambient temperature compared to equivalent single bendactuators. Shear Energizing the Can increase the Not readily 1985Fishbeck actuator causes a shear effective travel of applicable to otherUSP 4,584,590 motion in the actuator piezoelectric actuator material.actuators mechanisms Radial con- The actuator squeezes Relatively easyHigh force 1970 Zoltan USP striction an ink reservoir, to fabricatesingle required 3,683,212 forcing ink from a nozzles from glassInefficient constricted nozzle. tubing as Difficult to macroscopicintegrate with VLSI structures processes Coil/uncoil A coiled actuatorEasy to fabricate Difficult to IJ17, IJ21, IJ34, uncoils or coils moreas a planar VLSI fabricate for non- IJ35 tightly. The motion of processplanar devices the free end of the Small area Poor out-of-plane actuatorejects the ink. required, therefore stiffness low cost Bow The actuatorbows (or Can increase the Maximum travel IJ16, IJ18, IJ27 buckles) inthe middle speed of travel is constrained when energized. MechanicallyHigh force rigid required Push-Pull Two actuators control The structureis Not readily IJ18 a shutter. One actuator pinned at both ends,suitable for ink jets pulls the shutter, and so has a high out-of- whichdirectly push the other pushes it. plane rigidity the ink Curl A set ofactuators curl Good fluid flow Design IJ20, IJ42 inwards inwards toreduce the to the region behind complexity volume of ink that theactuator they enclose. increases efficiency Curl A set of actuators curlRelatively simple Relatively large IJ43 outwards outwards, pressurizingconstruction chip area ink in a chamber surrounding the actuators, andexpelling ink from a nozzle in the chamber. Iris Multiple vanes encloseHigh efficiency High fabrication IJ22 a volume of ink. These Small chiparea complexity simultaneously rotate, Not suitable for reducing thevolume pigmented inks between the vanes. Acoustic The actuator vibratesThe actuator can Large area 1993 Hadimioglu vibration at a highfrequency. be physically distant required for et al, EUP 550,192 fromthe ink efficient operation 1993 Elrod et al, at useful frequencies EUP572,220 Acoustic coupling and crosstalk Complex drive circuitry Poorcontrol of drop volume and position None In various ink jet No movingparts Various other Silverbrook, EP designs the actuator tradeoffs are0771 658 A2 and does not move. required to related patent eliminatemoving applications parts Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkrefilled. After the Operational force relatively jet actuator isenergized, simplicity small compared to IJ01-IJ07, IJ10- it typicallyreturns actuator force IJ14, IJ16, IJ20, rapidly to its normal Longrefill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillatingchamber is provided at Low actuator common ink IJ17, IJ18, IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and Mter theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate torefill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill Thermal ink jet channel to the nozzlechamber Operational rate Piezoelectric ink is made long and simplicityMay result in a jet relatively narrow, Reduces relatively large chipIJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01- pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22, IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle, area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, IJ05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofink jet, there is no problem is ink back-flow on 0771 658 A2 and doesnot expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most ink jet nozzlefiring fired periodically, complexity on the sufficient to systemsbefore the ink has a print head displace dried ink IJ01, IJ02, IJ03,chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09,IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20,IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26,IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, afterIJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to acleaning IJ39, IJ40, IJ41, station. IJ42, IJ43, IJ44, IJ45 Extra Insystems which heat Can be highly Requires higher Silverbrook, EP powerto the ink, but do not boil effective if the drive voltage for 0771 658A2 and ink heater it under normal heater is adjacent to clearing relatedpatent situations, nozzle the nozzle May require applications clearingcan be larger drive achieved by over- transistors powering the heaterand boiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used success-ion rapid succession. In extradrive circuits depends with: IJ01, IJ02, of actuator someconfigurations, on the print head substantially upon IJ03, IJ04, IJ05,pulses this may cause heat Can be readily the configuration of IJ06,IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzleIJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20,IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations,it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrationsto dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Notsuitable May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle HighIJ08, IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic. blockages. This is actuators easiestto achieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EPclearing plate is pushed against severely clogged mechanical 0771 658 A2and plate the nozzles. The plate nozzles alignment is related patent hasa post for every required applications nozzle. A post moves Moving partsare through each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required.

Description Advantages Disadvantages Examples NOZZLE PLATE CONSTRUCTIONElectro- A nozzle plate is Fabrication High Hewlett Packard formedseparately fabricated simplicity temperatures and Thermal Ink jet nickelfrom electroformed pressures are nickel, and bonded to required to bondthe print head chip. nozzle plate ♦Minimum thickness constraints♦Differential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, such as polyimide or is possible Slowwhere there pp. 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., USP lowcost head 5,208,604 May produce thin burrs at exit holes Silicon Aseparate nozzle High accuracy is Two part K. Bean, IEEE micro- plate isattainable construction Transactions on machined micromachined from Highcost Electron Devices, single crystal silicon, Requires Vol. ED-25, No.10, and bonded to the precision alignment 1978, pp 1185-1195 print headwafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins et al., USP4,899,181 Glass Fine glass capillaries No expensive Very small 1970Zoltan USP capillaries are drawn from glass equipment required nozzlesizes are 3,683,212 tubing. This method Simple to make difficult to formhas been used for single nozzles Not suited for making individual massproduction nozzles, but is difficult to use for bulk manufacturing ofprint heads with thousands of nozzles. Monolithic, The nozzle plate isHigh accuracy Requires Silverbrook, EP surface deposited as a layer (<1μm) sacrificial layer 0771 658 A2 and micro- using standard VLSIMonolithic under the nozzle related patent machined depositiontechniques. Low cost plate to form the applications using VLSI Nozzlesare etched in Existing nozzle chamber IJ01, IJ02, IJ04, litho- thenozzle plate using processes can be Surface may be IJ11, IJ12, IJ17,graphic VLSI lithography and used fragile to the touch IJ18, IJ20, IJ22,processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34,IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, Thenozzle plate is a High accuracy Requires long IJ03, IJ05, IJ06, etchedburied etch stop in the (<1 μm) etch times IJ07, IJ08, IJ09, throughwafer. Nozzle Monolithic Requires a IJ10, IJ13, IJ14, substrate chambersare etched in Low cost support wafer IJ15, IJ16, IJ19, the front of thewafer, No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26thinned from the back side. Nozzles are then etched in the etch stoplayer. No nozzle Various methods have No nozzles to Difficult to Ricoh1995 plate been tried to eliminate become clogged control drop Sekiya etal USP the nozzles entirely, to position accurately 5,412,413 preventnozzle Crosstalk 1993 Hadimioglu clogging. These problems et al EUP550,192 include thermal bubble 1993 Elrod et al mechanisms and EUP572,220 acoustic lens mechanisms Trough Each drop ejector has ReducedDrop firing IJ35 a trough through manufacturing direction is sensitivewhich a paddle moves. complexity to wicking. There is no nozzleMonolithic plate. Nozzle slit The elimination of No nozzles to Difficultto 1989 Saito et al instead of nozzle holes and become clogged controldrop USP 4,799,068 individual replacement by a slit position accuratelynozzles encompassing many Crosstalk actuator positions problems reducesnozzle clogging, but increases crosstalk due to ink surface waves DROPEJECTION DIRECTION Edge Ink flow is along the Simple Nozzles limitedCanon Bubblejet (‘edge surface of the chip, construction to edge 1979Endo et al GB shooter’) and ink drops are No silicon High resolutionpatent 2,007,162 ejected from the chip etching required is difficultXerox heater-in- edge. Good heat Fast color pit 1990 Hawkins et sinkingvia substrate printing requires al USP 4,899,181 Mechanically one printhead per Tone jet strong color Ease of chip handing Surface Ink flow isalong the No bulk silicon Maximum ink Hewlett-Packard (‘roof surface ofthe chip, etching required flow is severely TIJ 1982 Vaught et shooter’)and ink drops are Silicon can make restricted al USP 4,490,728 ejectedfrom the chip an effective heat IJ02, IJ11, IJ12, surface, normal to thesink IJ20, IJ22 plane of the chip. Mechanical strength Through Ink flowis through the High ink flow Requires bulk Silverbrook, EP chip, chip,and ink drops are Suitable for silicon etching 0771 658 A2 and forwardejected from the front pagewidth print related patent (‘up surface ofthe chip. heads applications shooter’) High nozzle IJ04, IJ17, IJ18,packing density IJ24, IJ27-IJ45 therefore low manufacturing cost ThroughInk flow is through the High ink flow Requires wafer IJ01, IJ03, IJ05,chip, chip, and ink drops are Suitable for thinning IJ06, IJ07, IJ08,reverse ejected from the rear pagewidth print Requires special IJ09,IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14,IJ15, IJ16, shooter’) High nozzle manufacture IJ19, IJ21, IJ23, packingdensity IJ25, IJ26 therefore low manufacturing cost Through Ink flow isthrough the Suitable for Pagewidth print Epson Stylus actuator actuator,which is not piezoelectric print heads require Tektronix hot fabricatedas part of heads several thousand melt piezoelectric the same substrateas connections to drive ink jets the drive transistors. circuits Cannotbe manufactured in standard CMOS fabs Complex assembly required INK TYPEAqueous, Water based ink which Environmentally Slow drying Most existingink dye typically contains: friendly Corrosive jets water, dye,surfactant, No odor Bleeds on paper All IJ series ink humectant, and Mayjets biocide. strikethrough Silverbrook, EP Modern ink dyes have Cocklespaper 0771 658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks aremedium can be used Printed pages USP 4,820,346 usually wax based, Nopaper cockle may ‘block’ All IJ series ink with a melting point occursInk temperature jets around 80° C. After No wicking may be above thejetting the ink freezes occurs curie point of almost instantly upon Nobleed occurs permanent magnets contacting the print No strikethrough Inkheaters medium or a transfer occurs consume power roller. Long warm-uptime Oil Oil based inks are High solubility High viscosity: All IJseries ink extensively used in medium for some this is a significantjets offset printing. They dyes limitation for use in have advantages inDoes not cockle ink jets, which improved paper usually require acharacteristics on Does not wick low viscosity. Some paper (especiallyno through paper short chain and wicking or cockle). multi-branched oilsOil soluble dies and have a sufficiently pigments are required. lowviscosity. Slow drying Micro- A microemulsion is a Stops ink bleedViscosity higher All IJ series ink emulsion stable, self forming Highdye than water jets emulsion of oil, water, solubility Cost is slightlyand surfactant. The Water, oil, and higher than water characteristicdrop size amphiphilic soluble based ink is less than 100 nm, dies can beused High surfactant and is determined by Can stabilize concentrationthe preferred curvature pigment required (around of the surfactant.suspensions 5%)

What is claimed is:
 1. A nozzle arrangement for an ink jet printhead,the nozzle arrangement comprising a wafer substrate having a nozzlechamber defined therein; a nozzle chamber wall that defines an inkejection port and a rim about the ink ejection port; and a series ofradially positioned actuators attached to the nozzle rim and extendingradially from the rim to form a portion of the nozzle chamber walladjacent the rim, each actuator being configured so that a radiallyouter edge of each actuator is displaceable into the chamber, uponactuation of the actuator and so that, upon such displacement, apressure within the nozzle chamber is increased, resulting in theejection of ink from the ejection port.
 2. A nozzle arrangement asclaimed in claim 1, wherein the actuators are configured to bend intothe nozzle chamber towards a centre of the nozzle chamber.
 3. A nozzlearrangement as claimed in claim 2, wherein each actuator comprises aconductive resistive heating element encased within a material having acoefficient of thermal expansion suitable for creating displacement ofthe actuator upon uneven heating of said material.
 4. A nozzlearrangement as claimed in claim 3, wherein the conductive resistiveheating element of each actuator is positioned within said material sothat uneven heating of said material results, causing the displacementof each actuator into the nozzle chamber.
 5. A nozzle arrangement asclaimed in claim 3, wherein the resistive heating element of eachactuator is serpentine to allow for substantially unhindered expansionof said material.
 6. A nozzle arrangement as claimed in claim 3, inwhich a number of struts interconnect said rim to said wafer substrate,each strut incorporating a power rail for supplying electrical power tothe conductive resistive heating element.
 7. An ink jet nozzlearrangement as claimed in claim 1, in which an ink inlet channel isdefined in said wafer substrate and is in fluid communication with thenozzle chamber.
 8. A printhead which comprises a plurality of ink jetnozzle arrangements as claimed in claim 1.